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avformat/format: Fix registering a format more than once and related races 

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2016-04-07 17:26:56 +02:00
parent a887fbb582
commit 4cc896ea5f
1 changed files with 10 additions and 6 deletions
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16
libavformat/format.c
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@ -62,20 +62,24 @@ void av_register_input_format(AVInputFormat *format)
{
AVInputFormat **p = last_iformat;
format->next = NULL;
while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format))
// Note, format could be added after the first 2 checks but that implies that *p is no longer NULL
while(p != &format->next && !format->next && avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format))
p = &(*p)->next;
last_iformat = &format->next;
if (!format->next)
last_iformat = &format->next;
}
void av_register_output_format(AVOutputFormat *format)
{
AVOutputFormat **p = last_oformat;
format->next = NULL;
while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format))
// Note, format could be added after the first 2 checks but that implies that *p is no longer NULL
while(p != &format->next && !format->next && avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format))
p = &(*p)->next;
last_oformat = &format->next;
if (!format->next)
last_oformat = &format->next;
}
int av_match_ext(const char *filename, const char *extensions)